TABLE OF CONTENTS 



xiu 



CHAPTER XVI 



THE ABSORPTIVE PROPERTIES OP SOILS .... 

 Substitution of bases, 251 Time required for absorp- 

 tion, 252 Insolubility of certain absorbed substances, 

 253 Influence of size of particle, 254 Causes of ab- 

 sorption, 255 Zeolites, 256 Chabazite, 257 Pres- 

 ence of zeolites questioned, 258 Absorption of phos- 

 phoric acid, 259 Formation of insoluble phosphates, 

 260 Absorption, 261 Absorption by colloids, 262 

 Absorptive properties of colloidal matter, 263 Selective 

 absorption, 264 Absorptive power of colloidal silicates, 

 265 Absorption by colloids versus absorption by zeo- 

 lites, 266 Absorption by organic matter, 267 Ab- 

 sorption of water vapor and of gases by soils, 268 

 Absorption of ammonia, 269 Absorption of carbon 

 dioxide, 270 Absorption of nitrogen and oxygen, 271 



Relation of temperature to gas absorption, 272 

 Relation of absorptive capacity to productiveness, 273 



Absorption as related to drainage, 274 Substances 

 usually carried in drainage water, 276 Drainage rec- 

 ords at Rothamsted, 276 Drainage records at Brom- 

 berg, 277 Losses of nitrogen and calcium, 278 

 Composition of surface water, 279. 



PAGES 



349-374 



CHAPTER XVII 



ACID OR SOUR SOILS 



Nature of soil acidity, 280 Positive acidity, 281 

 Negative acidity, 282 Production of sour soils, 283 

 Removal of bases by drainage as a cause for acidity, 284 

 Removal of bases by plants, 285 Effect of green 

 manures on acidity, 286 Effect of fertilizers on soil 

 acidity, 287 Acidity in relation to climate and to for- 

 mation of soil, 288 Weeds that flourish on sour soils, 

 289 Crops adapted to sour soils, 290 Crops that are 

 injured by acid soils, 291 Qualitative tests for acidity, 

 292 Litmus paper test, 293 Ammonia test, 294 

 Zinc sulfide test, 295 Litmus paper and potassium 

 nitrate, 296 Acid test for carbonates, 297 Plants as 



376-390 



